Currently, in storage apparatuses, a backup system that saves user data in a cache memory to a nonvolatile memory in order to protect the user data in the cache memory in the case of, for example, a power failure is known. For example, in an entry model storage apparatus, an electric double-layer capacitor (hereinafter referred to as a capacitor) is included, and, in the case of a power failure, user data in a cache memory is copied and saved to a nonvolatile memory using power supplied from the capacitor. Capacitors generally have longer lives than batteries, and the frequency of performing maintenance may be reduced by using such capacitors as backup power supplies.
Examples of the related art are disclosed in Japanese Laid-open Patent Publication No. 2005-332471 and Japanese Laid-open Patent Publication No. 2007-124782.